Critical Problem : Freeze Problem while Modeling in Blender 2.80 Beta
Watch your subdivision level:



6 is huge. Usually, you won't go over 2 or 3 in the viewport, and let the higher subdivision levels for the render only. Change that and you will have far fewer issues.
And considering your model, 3 really is enough.



Also, since you're using a mirror modifier, take advantage of it and model only half of your model. Right now you're modeling some parts only on one side, some other in both sides, it doesn't really make any sense, it doubles your work and the final result is messy.
You're using a solidify modifier to thickens your model, but most of your model has already some thickness. You should constraint the solidify effect on a vertex group.

Or, to solve both those issues at once: separate your model into several objects witch their own modifiers. Select your mesh parts needing thickness, press P and hit Separate selection. Let you solidify modifier on the new object, and remove it from the original.